It is priorly known to manufacture cable sheaths by the steps of continuously drawing a metal strip in a longitudinal direction through a plurality of forming rollers to form a hollow tubular sheath and then continuously welding the longitudinal abutting edges of the hollow tubular member. Further, it is known to form the metal strip around a cable core prior to the step of continuously welding the longitudinal abutting edges of the sheath. Additionally, it is known to include in such cable core a plurality of electrical and/or optical conductors.
Optical fibers priorly utilized in communication cables are notoriously known as being subject to mechanical damage as the result of tensional forces and small diameter bending. Consequently, numerous sheathing methods and apparatus have been priorly employed in an effort to protect the optical fibers from such forces and bending. One such method employed a corrugated metallic sheath formed about a conductor element comprised of a plurality of optical fibers. In such method, the conductor element was continuously drawn in a longitudinal direction at a speed greater than the speed at which a metallic strip was longitudinally drawn and formed about the conductor element. Another such method employed continuously drawing a metallic strip to which was bonded a conductor element comprised of a plurality of optical fibers. The metallic strip was formed into a tubular configuration about the conductor elements and a plurality of notches were formed in the circumferential direction, so that the sheath was shortened with respect to the encompassed conductor element.
Each of these known methods were expensive in execution, and the feature sought of having a conductor element length sufficiently greater than the length of the encompassing metallic sheath to avoid mechanical damage to the optical fibers, was not readily achieved. Such was the case especially with respect to the manufacture of optical conductor cables employed in submarine cables of extended lengths.